The invention has as its object a new process for obtaining chemical compounds that are obtained from polyunsaturated fatty substances, said compounds characterized by the presence, along the linear hydrocarbon-containing chain, of a branch of at least two carbon atoms.
These compounds are obtained by adding olefins to the polyunsaturated fatty substances that may or may not be conjugated, in the presence of an iron catalytic system.
The unsaturated codimers that are obtained can be hydrogenated, and saturated fatty substances that are characterized by a melting point that is generally below xe2x88x9230xc2x0 C., significant thermostability, and desired surfactant properties are then obtained.
The presence of branches in the fatty substance-based compounds, mainly when these branches are located toward the center of the linear chains that comprise 14 to 18 carbon atoms, is reflected by a certain number of remarkable properties, such as, for example:
The very significant lowering of the melting points, pour points, cloud points and a considerable increase of the viscosity of the branched fatty substances relative to the same linear compounds (unbranched). This property is used in, for example, the lubricants, fats, or plasticizers where esters of fatty substances, salts or esters of branched alcohols, whose acid may be organic or mineral, are used.
The reduction of the surface and interfacial tension, characteristics still sought in the field of surfactants and emulsifiers. This reduction makes it possible to obtain very low CMC (critical micellar concentration).
The inhibition of the crystallization of branched soaps that may or may not be mixed with standard soaps, which makes it possible to obtain transparent soaps.
An increase of the hydrophilicity, which makes the branched compounds more soluble or more wettable. A possible use would be to use quaternary salts of branched fatty acids in the emollients where the softening is on a par with a certain wettability.
A modification of the surface of the molecule, a surface that is characterized by gaps that are produced by the presence of branches. The cosmetic application of this property makes it possible to consider skin cream formulas that allow water vapor to pass, for example bases that consist of branched acid esters or even esters in which the acid and the alcohol are both branched.
The increased solubility of heavy metal salts with branched acids, which makes them soluble either in water or in certain organic solvents. The applications are multiple, such as drying agents in paints, like pigments, in the extraction of metals, anticorrosion where it is possible to use salts of calcium, alkanolamines, or even amines as active agents. Likewise, the branched acid salts offer a greater compatibility of certain mineral batches with polymers, which makes it possible to increase the ratio of feedstocks in the plastics.
The bactericidal or bacteriostatic effect that is more or less pronounced according to the nature of the bacteria and the number or the magnitude of the branches makes it possible to protect the creams from bacterial attack or to replace the quaternary salts in the formulations that may or may not be basic. Another use exists as an inhibitor of water evaporation where, for example, compounds such as a branched alcohol or a branched acid monoglyceride make it possible to delay the biodegradability and therefore to conserve the inhibitor.
The reaction of olefins with butadiene or other dienes has been known for a long time and was examined several times. The codimerization of butadiene with ethylene leads to 1,4-hexadiene; codimerization of ethylene with isoprene to methyl-3 hexadiene; and, finally, by codimerization of ethylene with piperylene, vinyl-2-pentene is obtained. Many catalysts are used to carry out these reactions. It is possible to cite, for example, rhodium, ruthenium, palladium, cobalt, iron, or nickel systems. Systems with a titanium base have been described (Connel, Laurence G.-Ann. N.Y. Acad. Sci. (73), 214, 143-9) to catalyze the formation of vinylcyclobutane from ethylene and butadiene.
U.S. Pat. No. 3,927,137 and German Patent Application DE-A-39 06 434 describe the use of catalytic systems with a base of iron salts combined with imine- or diimine-type ligands for codimerizing xcex1-olefins of low molecular weight with conjugated diolefins.
In contrast, the addition of an olefin to functional dienes has rarely been described. Patent U.S. Pat. No. 3,742,080 points out the possibility of adding ethylene to dienes, of which one or two hydrocarbon-containing chain ends are substituted by halogen atoms or alkoxy groups.
It is also known that an olefin can react on a conjugated diene or triene compound according to a Diels-Alder-type reaction. For example, R. E. Beal et Coll. [JAOCS 52, 400 (1975)] described the addition of ethylene to the polyunsaturated fatty substances by simple heating to a temperature of 290xc2x0 C. Thus, a compound that has an unsaturated cycle with 6 carbon atoms in its hydrocarbon-containing chain is obtained from methyl and ethylene linoleate. After hydrogenation, these compounds have advantageous properties. Their melting point, however, which is above 10xc2x0 C., is still too high to allow them to be used as lubricants.
Another method for obtaining branched compounds of fatty substances is known. It consists in reacting, according to a Wittig-type reaction, a ketone, such as, for example, the methyl ester of 12-oxo octadecanoic acid with an ylide, for example, the link P("PHgr")3xe2x95x90CHCH3, where "PHgr" represents a phenyl radical. The compound CH3(CH2)5C(xe2x95x90CHCH3) (CH2)10COOCH3, which can be hydrogenated into methyl ethyl-12-octadecanoate, is then obtained [see D. G. Chasin et Coll., Chem. Phys. Lipids (71) 6, 8-30].
In nature, the presence of branched saturated compounds of fatty substances that are found in Koch bacilli, for example, or, with another length of hydrocarbon-containing chain, in mutton fat has been pointed out.
Finally, it is known that the products that are referred to as xe2x80x9cisostearicxe2x80x9d contain traces of compounds that carry ethyl- or vinyl-type branches.
Recently, international patent applications WO-A-91/11428, 91-11427, 91/11426, and 91/11425 describe obtaining branched fatty substance compounds by a catalytic process. The addition of olefin, such as ethylene, propylene or butene-1, to the polyunsaturated fatty substance, a linoleic acid ester, for example, is catalyzed by a system with a base of rhodium, iridium, palladium, or ruthenium. The systems with rhodium, which are the only ones to have been described in an obvious way, are not very active, however.
U.S. Pat. Nos. 5,476,956 and 5,434,282 describe the use of a very specific rhodium catalytic system that makes it possible to accelerate the addition of olefin to the fatty substance dienes, particularly conjugated dienes, by a factor of 50 to 100. This process, however, is still very difficult to apply on a large scale due to excessive rhodium consumption.
FR-B-2 766 482, in the name of the applicant, describes a cobalt catalytic system that consists in reacting simple olefins, for example ethylene and propylene, in polyunsaturated esters, for example methyl linoleate, which may or may not be conjugated, to obtain branched esters. The branched compounds that are obtained can be hydrogenated and used, among other things, as lubricant bases. In this application, a process for obtaining a codimer is described. Co-catalysts can optionally be introduced, such as, for example, transition metals of iron, nickel, copper, rhodium or palladium type. These co-catalysts make it possible to catalyze the conjugation, if a start is made from an unconjugated polyenic ester and therefore to accelerate the reaction speed.
The main improvement that this invention provides consists in a very significant increase in reactivity that is obtained by use of a catalytic system with an iron base relative to the preceding system that used primarily a cobalt system. By working in the same conditions, 10 to 15xc3x97 more mono-addition products are obtained.
From an economical standpoint, the catalytic system that is described in this invention could turn out to be of great interest with a view to optional industrial development.
The so-called xe2x80x9cpolyunsaturated fatty substancexe2x80x9d compound that is employed in the reaction on which the process of the invention is based is generally a compound that comprises, on the one hand, at least two ethylene bonds, whereby these bonds can be conjugated or can be conjugated two by two, and, on the other hand, a carboxylic group such as the one that is present in fatty acids that have 18 to 26 carbon atoms. Litmus, safflower, fish, linseed, soybean, oiticica, cottonseed, colza, Chinese wood, nut, corn, linola, and grape seed oils and generally all the oils or their derived esters that comprise polyunsaturated compounds are conceivable as raw materials.
The diene, triene, or polyene fatty acids that are considered can be used as such or preferably in the form of their esters that are formed either from fatty acids or oils by reaction with monofunctional alcohols, such as methanol or ethanol, difunctional alcohols, such as neopentylglycol, trifunctional alcohols, such as trimethylolpropane, and polyfunctional alcohols, such as sorbitol, polyglycerols, pentaerythritol and sugars. The oils themselves are possible substrates.
These esters can be used as they are or partially and/or totally conjugated. In other words, they can contain at least two double ethylene bonds that may or may not be separated by a methylene group. Among the best-known processes for conjugating double bonds, it is possible to cite those that use alkaline alcoholates in the presence or absence of a solvent. It is possible in this case to obtain up to 99% of fatty substance that is conjugated relative to the polyunsaturated fatty substance that is initially present in the oil.
Other conjugating catalytic systems that employ ruthenium or carbonyl iron complexes are known. The iron system can itself be conjugating in some cases. It is possible, however, to attach a co-metal to it to accelerate the conjugation reaction.
The monoolefinic compound that is employed in the reaction may consist of any reactive olefin that is selected from among the ordinary monoolefins (monoolefinic hydrocarbons), such as, for example, ethylene, propylene, or butene-1.
The object of this invention is therefore a new process for obtaining a branched fatty substance, in the form of a codimer, that is characterized in that at least one monoolefinic compound is added to a fatty substance that comprises at least two ethylene bonds that may or may not be conjugated, in the presence of a catalytic system that comprises at least one iron compound, at least one reducing compound, and at least one ligand that contains phosphorus, arsenic, antimony or nitrogen.
The iron compound can be a bivalent or trivalent inorganic or organic iron compound that corresponds to the formula Fe Xn, in which n=2 or 3, and X represents a halide, a thiocyanide, a sulfate, a nitrate, an alcoholate, a carbonate, a carboxylate, a diketone, a betacetocarboxylic acid ester, a hydroxyl, an alkyl or alkenyl group (in the organo-iron compounds) or else a hydride. Particular examples of usable iron compounds are iron(II) bisacetylacetonate, iron(III) trisacetylacetonate and iron(II) and (III) octoate.
The usable iron reducing compounds are most often selected from among:
the organoaluminum compounds of general formula AIRX(X)3-X1 where R is hydrogen or an alkyl group, for example methyl, ethyl, isopropyl, butyl, isobutyl or terbutyl, or an alkoxy group; X is a halogen atom; and x is equal to 1 or 2,
the organo-magnesia, aluminoxanes, sodium borhydride and varied alkaline hydrides, such as LiAlH4 and NaAlH4 themselves or their derivatives that are obtained by substituting 1 to 3 hydrogen atoms per 1, 2 or 3 alkoxy groups, for example LiAlH3(OR), LiAlH2(OR)2 and LiAlH(OR)3, where R is an alkyl group, for example, methyl, ethyl, isopropyl, butyl, isobutyl or terbutyl.
The ligand can be selected:
from among the derivatives of phosphorus, arsenic or antimony that correspond in general to the formulas:
YRmX3-m, R2Yxe2x80x94(CH2)nxe2x80x94YR2, Y(OR)3 and YOR3, 
in which Y=P, As or Sb; m=0, 1, 2, or 3; R=alkyl, aryl or substituted aryl; X=halogen, and n=0, 1, 2, 3 or 4; and
from among the nitrogen-containing ligands, such as the amines and polyamines, imidazole, the substituted imidazoles, pyrrole and the substituted pyrroles, pyrazoles, amidic derivatives, imines or diimines (produced, for example, by reaction of glyoxal with a derivative of the aniline that is substituted on the aromatic core), and finally the pyridinic derivatives.
Particular examples of ligands are those that have for general formulas:
Rxe2x80x94Nxe2x95x90CRxe2x80x2xe2x80x94CRxe2x80x2xe2x80x94Nxe2x80x94R, PR3 and R2Pxe2x80x94(CH2)nxe2x80x94PR2 
with Rxe2x80x2=H or CH3, n=1, 2, 3 or 4 and R=alkyl, aryl or aryl that is partially substituted by 1, 2, 3 or 4 methyl, ethyl, isopropyl or methoxy groups.
The following developed formulas illustrate some of these products: 
It is optionally possible to use an organic compound that acts as a solvent; as solvents, it is possible to use the aliphatic or aromatic hydrocarbons, the ethers, esters, halogenated hydrocarbides and, at low concentration, sulfoxides and amides; the reaction can also be carried out in the absence of added solvent; it is then the ester of which a portion does not react with the olefin that acts as a solvent.
It is also possible to add to the codimerization catalyst a salt of another transition metal (for example, Co, Ni, Cu, Rh, Pd, Mn, Mo, W or V, preferably Ni, Cu, Rh or Pd), which is introduced in a smaller proportion compared to the iron and which makes it possible to accelerate the reaction, in particular when the polyunsaturated substrate with a fatty substance base does not have its double bonds in conjugated form.
The molar ratio between the ligand and the iron compound is preferably from 0.5 to 10, in particular from 0.5 to 3.
If the ligand is monocoordinating, there is an advantage in using it with a ligand/metal molar ratio of 2 to 3. If the ligand is bicoordinating, it will rather be used with a molar ratio of 1 to 1.5. The molar ratio between the reducing agent and the iron compound is generally 1 to 30, preferably 7 to 15.
According to this invention, it is possible to preform the catalytic system by reacting the iron salt, the ligand, and the reducing agent, and then to introduce it into the polyunsaturated fatty substance in the presence of the olefin.
Generally, it is preferable to add the ligand to the iron compound in the presence of unsaturated fatty substance and in the presence of olefin before the reducing agent is added. It is also possible to isolate a small complex of FeHXL2 iron (where L is an imine and X is a halogen) or FeHXLxe2x80x2 (where Lxe2x80x2 is a diimine and X is a halogen) and to add a reducing agent such as an alkylaluminum or the like in the presence of the polyunsaturated fatty substance.
The catalytic composition is added to the system in a catalytic amount. This amount is expressed as being 10xe2x88x924 to 10xe2x88x921 mol of iron per mol of conjugated polyunsaturated fatty substance. The reaction temperature is 40 to 120xc2x0 C. and preferably 50 to 70xc2x0 C. The olefin pressure is 0.1 to 30 MPa, and preferably 2 to 5 MPa. The reaction times depend on the concentration and the nature of the catalyst. The reaction times can be short, for example from several minutes to several hours.
It is possible to operate according to a continuous or intermittent process. The introduction of the catalyst and esters into the reactor can be done in the presence of ethylene at low temperature or at the highest temperature directly into the reactor.
The branched fatty substances that are obtained can be hydrogenated to obtain more stable products. The hydrogenation of the olefinic compounds is carried out with a catalyst that is known for hydrogenating olefins, either, for example, Raney nickel, palladium on carbon or a supported nickel, generally after the codimerization catalyst has been eliminated by washing with water. It is sometimes possible to use the codimerization catalyst as a hydrogenation catalyst. After hydrogenation, the unbranched saturated compounds are eliminated by crystallization or by distillation. It is also possible to distill before hydrogenation to concentrate the branched products.
The branched esters can be used as bases for surfactants, emulsifiers, emollients, lubricants or can undergo other treatments, such as transesterification with heavier alcohols when methyl esters are involved initially. It is also possible to transform them into their heavy metal salts.
The following examples illustrate the invention; they are not limiting.